1. Field
A scroll compressor is disclosed herein.
2. Background
In general, a compressor is a device that compresses a fluid, such as a refrigerant gas, and may be classified as a rotary compressor, a reciprocating compressor, or a scroll compressor, for example, according to a method for compressing a fluid. The scroll compressor is a high-efficiency, low-noise compressor, which is widely applied in the field of air conditioners. The scroll compressor is configured such that an orbiting scroll having a wrap (hereinafter, referred to as an “orbiting wrap”), and a non-orbiting scroll having a wrap (hereinafter, referred to as a “non-orbiting wrap”) engaged with the orbiting wrap perform a relative orbiting motion. In the scroll compressor a plurality of compression chambers including a suction chamber, an intermediate pressure chamber, and a discharge chamber is formed between the orbiting wrap and the non-orbiting wrap. A volume of the plurality of compression chambers is decreased as the plurality of compression chambers continuously move in a central direction during a process in which the orbiting scroll and the non-orbiting scroll perform a relative orbiting motion, so that a refrigerant is continuously sectioned in, compressed, and discharged.
The scroll compressor can be divided into a closed-type scroll compressor, in which a compression mechanism and an electric motor are installed together in a closed casing, and an open-type scroll compressor in which a compression mechanism operated by an external drive is installed in a casing.
Hereinafter, an open-type scroll compressor will be described.
FIG. 1 is a sectional view of a conventional open-type scroll compressor. As shown in FIG. 1, in the conventional open-type scroll compressor, a main frame 2 is installed in an internal space of a casing 1, and a first end of a drive shaft 3 is inserted into the main frame 2 to be rotatably coupled to the main frame 2.
An orbiting scroll 4 is coupled to a second end of the drive shaft 3, and a non-orbiting scroll 5 is coupled to the orbiting scroll 4. The non-orbiting scroll 5 is coupled to the main frame 2 with the orbiting scroll interposed therebetween. An orbiting wrap 4a and a non-orbiting wrap 5a are formed at or on the orbiting scroll 4 and the non-orbiting scroll 5, respectively. The orbiting wrap 4a and the non-orbiting wrap 5a form a plurality of compression chambers P including a suction chamber, an intermediate pressure chamber, and a discharge chamber when the orbiting wrap 4a is rotated with respect to the non-orbiting wrap 5a. 
A suction port 5b that communicates with the suction chamber is formed at one side of the non-orbiting scroll 5, a discharge port (not shown) that communicates with the discharge chamber is formed at a center of the non-orbiting scroll 5, and an intermediate pressure hole 5c that communicates with the intermediate pressure chamber is formed between the suction port 5b and the discharge port (not shown) of the non-orbiting scroll 5. The suction port 5b communicates with a suction space 1a of the casing 1 to which a suction pipe 11 is connected. The discharge port (not shown) communicates with a discharge space 1b of the casing 1 to which a discharge pipe (not shown) is connected. The intermediate pressure hole 5c communicates with a capacity varying unit or device 9.
The capacity varying unit 9 includes a first bypass pipe 91 that communicates with the intermediate pressure hole 5c, a second bypass pipe 92 that communicates with the suction pipe 11, and an opening/closing valve 93 that provides communication between the first bypass pipe 91 and the second bypass pipe 92 or blocks communication between the first bypass pipe 91 and the second bypass pipe 92. A first end of the first bypass pipe 91 communicates with the intermediate pressure hole 5c at an inside of the casing 1 by passing through the casing 1 and a second end of the first bypass pipe 91 communicates with the opening/closing valve 93 outside of the casing 1. A first end of the second bypass pipe 92 communicates, with the suction pipe 11 outside of the casing 1 and a second end of the second bypass pipe 92 communicates with the opening/closing valve 93. The opening/closing valve 93 is provided outside of the casing 1.
While the first end of the drive shaft 3 is supported by the main frame 2, a circumference of the second end of the drive shaft 3 is supported by a sub-frame 6 coupled to the main frame 2. A thrust surface 2b that supports the orbiting scroll 4 in a shaft or axial direction and a shaft hole 2d through which the drive shaft 3 passes are formed at the main frame 2.
A front cover 7 that forms a portion of the casing 1 is coupled to the sub-frame 6, and an oil pump 8 that pumps oil stored in the casing 1 to a sliding portion and a compression mechanism is installed in the front cover 7. The oil pump 8 is coupled to the second end of the drive shaft 3, and the drive shaft 3 is coupled to a drive pulley 3b provided outside of the casing 1 by passing through the front cover 7. The drive pulley 3b, for example, is connected to an external drive source (not shown) driven by gas to drive the compression mechanism when necessary.
In the conventional scroll compressor described above, the drive pulley 3b is connected to the external drive source (not shown), so that an external drive force is transmitted to the compression mechanism through the drive shaft 3. Then, the orbiting scroll 4 coupled to the drive shaft 3 performs an orbiting motion by an eccentric distance in a state in which the orbiting scroll 4 is supported by the main frame 2, and simultaneously, the plurality of compression chambers P including the suction chamber, the intermediate pressure chamber, and the discharge chamber are successively formed between the rotating wrap 4a and the non-orbiting wrap 5a. A volume of the plurality of compression chambers P is decreased as the plurality of compression chambers P are continuously moved in a central direction by a continuous orbiting motion of the orbiting scroll 4, so that a refrigerant that flows into the suction space 1a of the casing 1 is continuously sectioned, compressed, and discharged into the discharge space 1b of the casing 1.
Also, in the conventional scroll compressor, a compression capacity is varied by the capacity varying unit 9. That is, as opening/closing value 93 allows the first bypass pipe 91 and the second bypass pipe 92 to communicate with each other, a refrigerant in the intermediate pressure chamber is bypassed into the suction space 1a via a bypass flow path including the intermediate pressure hole 5c, the first bypass pipe 91, the opening/closing valve 93, the second bypass pipe 92, and the suction pipe 11. Accordingly, a partial load operation in which the compression capacity is decreased can be performed. On the other hand if the opening/closing valve 93 blocks the communication between the first bypass pipe 91 and the second bypass pipe 92, the bypassing of the refrigerant is stopped. Thus, the refrigerant in the intermediate pressure chamber is compressed without being leaked through the intermediate pressure hole 5c, and accordingly, a full load operation in which the compression capacity is not decreased can be performed.
However, in the conventional scroll compressor described above, the capacity varying unit 9 for varying the capacity of the compressor is exposed outside of the casing 1. That is a portion of the first bypass pipe 91, the opening/closing valve 93, and the second bypass pipe 92 are exposed outside of the casing 1. Therefore, as the bypass flow path is lengthened, a pressure loss is increased. In addition, refrigerant is leaked outside of the compressor from each connection portion, that is, a connection portion between the first bypass pipe 91 and the casing 1, a connection portion between the first bypass pipe 91 and the opening/closing valve 93, a connection portion between the opening/closing valve 93 and the second bypass pipe 92, or a connection portion between the second bypass pipe 92 and the suction pipe 11, and a size, weight, and manufacturing cost of the compressor are increased.
Also, as the opening/closing valve 93 directly opens and closes the bypass flow path, the conventional scroll compressor should be operated while enduring a pressure of the bypassed refrigerant, which requires a considerable operating force. Therefore, a considerable power is required to vary the capacity of the compressor.